1. Field of the Invention
The present invention relates to a wiring substrate, and to a method for producing the wiring substrate.
2. Description of Related Art
In one type of wiring substrate, connection terminals (pads) have thereon a solder ball. In the wiring substrate, an opening through which at least a portion of the connection terminal is exposed is formed in the outermost layer of solder resist, a flux and a solder ball are charged into the opening of the solder resist layer, and the connection terminal is electrically connected to the solder ball through reflow soldering.
In recent years, with the rapid progress of miniaturization of semiconductor packages, the number of connection terminals for a semiconductor chip sealed in a semiconductor package has increased. Therefore, the distance between connection terminals (pads) of a wiring substrate on which such semiconductor chips are mounted is reduced, and the bore diameter of an opening of a solder resist film through which the connection terminal is exposed is also reduced. Thus, there is a high likelihood that the opening fails to be provided with a solder ball; i.e., a high likelihood of the occurrence of a missing ball(s).
In connection therewith, there has been proposed a technique in which a guide portion having an opening whose bore diameter increases with the distance from a connection terminal increases is provided on a solder resist film for guiding a solder ball into the opening of the solder resist film (see, for example, Patent Document 1).